Hypoxia-What Is It, Do We Affect
It, And How Might Our Future
Affect It?
Rick Cruse
Hypoxia – What is it?
Hypoxia – What it is not?
Hypoxia – What is it?
An area of low dissolved oxygen
concentrations that cannot support marine
life. Typically O2 < 2 ppm
Hypoxia – Where does it occur?
Hypoxia – Where does it occur?
Hypoxia – Why does it occur?
 Freshwater
and saltwater stratify
Hypoxia – Why does it occur?
 Algae
bloom in freshwater
 Algae settle to bottom
 Algae decomposition consumes O2
Hypoxia – Where (at what
depth) does it occur?
www.gulfhypoxia.net/Research/
Hypoxia – How large an area?
x
http://www.epa.gov/gmpo/pdf/2007-hypoxia-pred-web-5.pdf
Turner and Rabalais, 2007
X – size in 2008
Hypoxia - Why does it occur?
Hypoxia – Why does it occur?
Algae Yield
Algae Yield and N fertilization
Hypoxia – Is nutrient flux constant?
co.water.usgs.gov
Hypoxia – Why Iowa connection?
NO3-N Concentration (mg/L)
NO3-N Concentration in the Raccoon River at Des Moines
20.00
18.00
16.00
14.00
12.00
10.00
8.00
6.00
4.00
2.00
0.00
Annual Max
Annual Mean
1972
1977
1982
1987
1992
1997
2002
Data provided by Chris
Jones Des Moines Water
Works
Nitrate load in Raccoon River jumps, climate change?
Hypoxia – Why Iowa connection?
First Quarter NO3-N Load, Raccoon River
at Des Moines
2007
2006
2005
2004
2003
2002
2001
2000
1999
9000
8000
7000
6000
5000
4000
3000
2000
1000
0
1998
tons Nitrogen
Raccoon River 1st Quarter Loads-Revised
Data provided by Chris Jones Des Moines Water Works
Hypoxia – Why Iowa
connection?
20 – 25 lb/A
www.umces.edu/President/hypoxia.htm
Hypoxia – Why Iowa connection?
Look to the Future
Planted area: Corn, wheat, and soybeans
Million acres
100
90
Corn
80
Soybeans
70
60
Wheat
50
40
1980
1985
1990
1995
2000
2005
Source: USDA
Agricultural
Projections to Projections
2016, February 2007.
USDA
Agricultural
to
Economic Research Service, USDA.
2010
2015
2016
D. R. Keeney
Corn/Soybean and Perennial
Nitrate-N Concentrations in Tile
Drain

Tile drainage system
 U of MN - Lamberton
Gyles Randall, 2003
25
20
15
10
mg/L
Midpoint
of range
5
0
Corn/Bean Perennials
D. R. Keeney
Tom Kaspar
Rye after corn silage
Tom Kaspar
Cumulative annual nitrate-N load of drainage
water for 2002-2005
90
81.1
Annual nitrate-N load (kg/ha)
80
Control
Rye Cover Crop
70
60
50.8
47.2
50
40.4
40
30
20
34.4
33.9
23.0
19.8
11.1
11.2
10
0
2002
2003
2004
2005
Kaspar et al., JEQ 36:1503-1511
Avg.
Iowa Daily Erosion Project
 Estimates
daily soil erosion, runoff and
soil moisture for the state of Iowa




Daily estimations since 2002
Published in Jan/Feb 2006 Journal of the
Soil and Water Conservation Society
Served on the web at
http://wepp.mesonet.agron.iastate.edu
Parameterizes WEPP erosion model with
radar rainfall, climate stations, and NRI
Simulated crops

Eight scenarios based on ISU research
Rotation
Tillage
Residue
Removal
Cover
Crop
Abbreviation
NRI
NRI
No
No
NRI
Corn/Soy
Min-till
No
No
CS-MT
Cont. Corn
Min-till
Yes
No
CC-MTRR
Corn/Soy
No-till
No
No
CS-NT
Cont. Corn
No-till
No
No
CC-NT
Cont. Corn
No-till
Yes
No
CC-NTRR
Cont. Corn
No-till
Yes
Yes
CC-NTRRCC
Switchgrass
No-till
Yes
No
Sw-NTRR
NEXRAD – Aug 22, 2007
Statewide mean precipitation: 1.56 in.
Switchgrass – NT, RR
Sw-NTRR
CC-NT
CS-NT
CC-NTRR
CC-NTRRCC
NRI
CS-MT
CC-MTRR
Cont. Corn – NT
Sw-NTRR
CC-NT
CS-NT
CC-NTRR
CC-NTRRCC
NRI
CS-MT
CC-MTRR
Corn/Soybean – NT
Sw-NTRR
CC-NT
CS-NT
CC-NTRR
CC-NTRRCC
NRI
CS-MT
CC-MTRR
Cont. Corn – NT, RR
Sw-NTRR
CC-NT
CS-NT
CC-NTRR
CC-NTRRCC
NRI
CS-MT
CC-MTRR
Cont. Corn – NT, RR, CC
Sw-NTRR
CC-NT
CS-NT
CC-NTRR
CC-NTRRCC
NRI
CS-MT
CC-MTRR
NRI Projected Rotation
Sw-NTRR
CC-NT
CS-NT
CC-NTRR
CC-NTRRCC
NRI
CS-MT
CC-MTRR
Corn/Soy - MT
Sw-NTRR
CC-NT
CS-NT
CC-NTRR
CC-NTRRCC
NRI
CS-MT
CC-MTRR
Cont. Corn - MTRR
Sw-NTRR
CC-NT
CS-NT
CC-NTRR
CC-NTRRCC
NRI
CS-MT
CC-MTRR
Event Summary
Management
8/22/2007 Mean Loss
(tons/acre)
8/22/2007 Mean
Runoff (in)
Sw-NTRR
0.044
0.657
CC-NT
0.113
0.662
CS-NT
0.184
0.651
CC-NTRR
0.230
0.649
CC-NTRRCC
0.232
0.650
NRI
0.320
0.640
CS-MT
0.406
0.647
CC-MTRR
0.458
0.646
Concluding Thought
OR